Communications networks are known that use a passive optical network to connect a transport network, such as the telephone transport network, to access terminals, such as end user terminals (e.g., see European Patent Application No. 1061764). As described in this reference, the passive optical network contains a bundle of N optical fibers and each of the fibers connects to a plurality of access terminals. Each single optical fiber is able to carry light of a number of M different communication wavelengths, so the network is capable of transmitting information at a number M of wavelengths in each fiber. Since a passive optical network is used, information may be transported to or from a terminal through the N optical fibers.
This type of network may employ statistical multiplexing of the use of the optical fibers and wavelengths to provide a large information transport capacity at relatively low cost. Statistical multiplexing is based on the activity pattern that is characteristic of access terminals. These terminals are only active intermittently and, as a result, only need a low transport capacity on average. However, when active, an access terminal may need a maximum transport capacity that is much larger than the average capacity. This allows multiplexing of the use of fibers and wavelengths between terminals, fibers and wavelengths being allocated to specific access terminals only when needed. Thus, much less capacity is needed than the product of the maximum capacity per access terminal and the number of access terminals, although each individual terminal may use the maximum capacity from time to time.
Although the assignment of terminals to times of transport and wavelengths is addressed in the aforementioned patent application, prior art arrangements do not address the way that light of different wavelengths is optically provided in the different fibers in such a network. One possible way to do this would be to provide a set of M light sources, light modulators and light demodulators for M different wavelengths for each of the N optical fibers. However, such a solution is expensive because it would require a large number (N×M) of light sources, light modulators and light demodulators.